The Inner Planets Payson Wilde EGR-491-A 9-19-19

The Inner Planets Venus Mercury

Etymology of Venus It is named after the Roman deity Mercury, the messenger of the gods. Mercury was one of five planets that the Romans knew of. It was named Mercury as it moved the fastest around the Sun.

Basic Info: Mercury Mercury is the innermost planet from the Sun. Mercury is also the smallest planet, with an average diameter of around 4,900 kilometers. Its surface gravity is only 38% of that of Earth. It is around 36 million miles (0.38 au) away from the Sun and 48 million miles (.51 au) away from Earth

Planetary Rotation Mercury is almost tidally-locked, meaning that one side of Mercury faces the Sun for most of its revolutions. It has a 3:2 spin-orbit resonance, meaning that it only rotates 3 times for every 2 revolutions around the Sun. Taking into account orbital motion, this means if you were on Mercury, you would only see 3 days every 2 years.

Planetary Orbit Mercury’s revolution around the Sun takes only 87.97 days. It has the shortest and fastest orbit around the Sun. Shape of the orbit is an oval.

Composition One of four terrestrial planets in the Solar System. Second densest planet after Earth. Mercury has a silicate crust with a most likely both a liquid and solid core. Mercury’s density implies that its core is large and composed of iron.

Surface Conditions The temperature of Mercury’s surface ranges from -180 °C to 425 °C This makes it the most extreme temperature change in the Solar System Mercury’s surface is covered in craters as it is very old.

Interesting Facts The stars behind it would go by moving three times faster. Standing on Mercury, the whole heliosphere is visible due to the lack of an atmosphere and almost negligible magnetic field. No one was sure of what Mercury looked until Mariner 10 flew by it in 1974. The only other probes sent to Mercury are MESSENGER (2013) and BepiColombo (will arrive in 2024).

How to View Mercury Mercury is the least observed planet due to its proximity to the Sun. Mercury is best observed in the Northern Hemisphere during the evening in April and May, and during the morning in October and November. At this time, it may appear as a bright star-like object, but is often far more difficult to observe than Venus, as it is farther away and closer to the Sun. Attempting to observe Mercury during the day can be dangerous, due to its proximity to the Sun. You can see Mercury’s transit (path in front of the Sun) on November 11th this year. They occur around 13 times every 100 years. The safest way to view the Mercury transit across the Sun yourself is to buy a purpose-built solar projection box.

Mercury Transit Viewings (Nov. 11, 2019)

Etymology of Venus Named after Roman goddess of love and beauty. The planet named after a female god. May have been named due to its much brighter appearance in the sky than other planets.

Basic Info: Venus It is 95% the size of Earth (around 7,500 km), and has 90% the surface gravity of Earth. Venus is 67.24 million miles (.72 au) from the Sun, and 25 million miles (.27 au) away from Earth.

Planetary Orbit and Rotation Venus takes 225 days to orbit the Sun. Rotation period of 243 Earth days, longer than any other planet. Rotates in the opposite direction to other planets (except Uranus). Planetary Orbit and Rotation

Composition Terrestrial planet. 81.5% of Earth’s mass. Similar crust-mantle-core composition to Earth. Lacks tectonic activity.

Surface Conditions Densest atmosphere, which consists of 96% CO2. 92 times the atmospheric pressure and average temperature 462°C. High volcanic activity and clouds of sulfuric acid, and lava channels thousands of kilometers long.

Exploration of Venus It was the first planet beyond Earth visited by a spacecraft (Mariner 2) in 1962. It was the first planet to be reached by a spacecraft when Venera 3 crashed on its surface in 1966. It was the first to be successfully landed on by Venera 7 in 1970. Has detailed images of the surface due to the radar mapping and UV photos of Venera 15, Venera 16, and Magellan probes.

Interesting Facts Venus was the first planet to be plotted across the sky, around 2000 BC. There may have had liquid water in the past. Data suggests lightning may occur in Venus’s atmosphere. Venus is actually shown in Van Gogh’s Starry Night.

How to View Venus Venus is the second-brightest natural object in the night sky after the Moon. Best seen in the summer (for the Northern Hemisphere, usually in May) at sunrise and sunset. This is because it will reach a higher altitude in the sky and appear further from the Sun, making it more visible against a darker sky. Transits of Venus only occur around every 243 years. “On September 30th, 2019, Venus sets about 30 minutes after the sun for viewers at latitude 40° north.  But the planet is only about 5° high at sunset.” -https://www.space.com/33619-visible-planets-guide.html

Questions?

References https://solarsystem.nasa.gov/planets/mercury/overview/ https://nineplanets.org/mercury.html https://www.space.com/mercury-not-so-elusive-february-2019-sky.html https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is- planet-mercury-k4.html https://www.nasa.gov/mission_pages/messenger/main/index.html http://www.planetary.org/multimedia/space-images/venus/global-view-of- venus-from.html https://www.nasa.gov/venus/ https://www.space.com/44-venus-second-planet-from-the-sun-brightest-planet- in-solar-system.html https://www.universetoday.com/14246/how-to-find-venus-in-the-sky/